2009/01/04

I had lying around an old Konica lens, completely manual, which has not been used for a long time. To be precise, it is a "Konica Zoom-Hexanon AR 35-70 mm / F3.5-4.5", nothing fancy for nowadays standards, but Konica lenses enjoyed a good reputation at their moment. As I do not like to trow away things that still work, I am trying to make it work with my Canon EOS camera. In this first article, I explain how thins lens must be modified as not to break the camera.

Warnings

First of all, I must warn that this procedure may render your lenses unusable, because we are going to modify them. Personally, that is something that does not worry me, as I have not used mine for several years, and I am quite sure that it will not be used again unless I am capable of adapting it. Anyhow, the procedure described here is expected to break only the automatic diaphragm control (AE).

My second warning is that, once mounted on a Canon camera, the lens will not be able to focus to infinity. This happens because the distance between the back of the lens and the film plane was very short in the original Konica camera; this lens cannot enter that much into a Canon camera. Again, that is not a problem for me, as I have the intention to use this lens exclusively for macro-photography, using extension rings.

The procedure

This photo shows the lens before the modification. On the right picture, the two levers that these lenses have at the back can be seen: the first one (black and fixed), tells the camera the maximum aperture that this lens supports; the second one (chromed and movable) is used by the camera to set the diaphragm. Both levers must be removed prior to placing the lens in front of a camera, or they will clash with the internals of the camera.

Another (optional) modification I performed was to remove the diaphragm locking mechanism. To use this lens in auto mode, the diaphragm ring must be placed on the AE position, where it locks (on the left picture, a small lever can be seen on the diaphragm ring, used to unlock it). After the modification, this AE mode will not be used again, so this lock is just a nuisance.

Let's get started

First step is to take apart the metal piece at the back of the lens; the four screws shown on this photograph must be removed:

Next is the diaphragm ring, paying special attention to the small metal part shown on this picture; well, I suppose that there was a small metal part there, because I must admit I lost it. Without that piece, the diaphragm ring will move freely, and will not stop on the f marks.

Once the ring is out, we can now remove the locking mechanism; just push the small axis with a needle until it exits; we will have now these parts:

The ring can go back to the lens now. And we return to the back cover, because we need to remove the black central part; just unscrew the three screws that hold it and push forward (mine was a bit struck, perhaps even glued). Just two screws more and we can remove the lever that controls the diaphragm:

Last thing to remove is the black lever; this part is made of plastic, and was very easy to cut:

Finally, we can mount the lens again and it is ready to go.

We cannot put this lens on a Canon EOS camera directly, of course; but on next chapter I will explain how to create an adapter ring.